Electromagnetic switch



Ma 12, 1936. A H AMB 2,040,389

ELECTROMAGNETI G SWI TCH Filed Nov. 14, 1951 3 Sheets-Sheet l x7 on 7%? KO. 3. 79 MM May 12, 1936. A. Hf LAMB 2,040,339

ELECTROMAGNETIC SWITCH Filed Nov'. 14, 1951 3 sneets-sn e't 5 \illlllllllllllll Patented May 12, 1936 UNITED STATES ELECTROMAGNETIC SWITCH Anthony H. Lamb, Elizabeth, N. J.', assignor to Weston Ff ctrical -Instrument Corporation, Newark, N. J., a corporation of New Jersey Application November 14, 1931, Se'rial No. 575,067

7 Claims. (Cl. 200-87) electromagnetic switch in which the operating force established by a given'current flow is approximately constant throughout the major portion of the range of movement of the armature, i

and increases rapidly during the final movement of the armature. A further object is to provide a switch including an'electromagnet having a relatively high ratio of the current value at which the armature will drop away from the pole piece to the minimum current value efiective to attract the armature, thereby rendering the switch sensitive to relatively small changes in current flow. More specifically, an object is to provide an electromagnetic switch in which the magnet has a pair of pole pieces between which an armature is mounted for oscillatory movement, one of said pole pieces having angularly disposed faces upon or adjacent which an end and a side face, respectively; of the armature are disposed when the magnet is energized. Further specific objects are to provide relays which include mercury switches mounted directly on the relay armature, the arrangement being such that the mercury switch is tilted, but not lifted, by the armature. Theseand other objects of the invention will be apparent from the following specification, when taken with the accompanying drawings, in which,

Fig. 1 is a diagrammatic view illustrative of the invention,

Fig. 2 is a somewhat generalized central section through an embodiment of the invention,

Fig. 3 is a side elevation, with parts shown in section, of a relay including tilting contact switches,

Fig. 4 is a plan view of the same, but'with the parts in the positions they assume when the relay is energized, Y

, Figs; 5 and 6 are similar side and front elevations, respectively, of a relay carrying another arrangement of tilting switches, the wiring dia gram of the circuit being superposed on the Fig. 6 elevation 01' the relay, 7

Figs. '1' and 8 are plan and front elevations,

respectively, of a relayhaving adirect contact switch, and

Fig. 9 is a fragmentary side view of the armature and contact switch with the parts approaching one limit of the armature movement. 5 In the drawings, the numeral 1 identifies the magnet core which preferably is of U-shape, having an end section and parallel side members which terminate in poles between which the armature 2 is carried on a pivot 3 for rocking move- 10 ment. When the magnet is energized, the armature is moved to the position shown in Fig. i, one end of the armature being received within the deep notch or seat formed in one side memher by the pole face 4 which extends across the path of movement of the armature end, and the pole face 5 which extends substantially parallel to its path of movement.

The solenoid includes the operating winding 6 and the non-inductive winding 1 which are conn'ected in parallel across the relay terminals 3. One application of the relay is indicated in Fig. 1, in which the sensitive or primary relay 9 kn cludes a contact arm to for cooperation with a fixed contact 45 to close the circuit from a current source l2 to the terminals 8 of the relay.

Upon'opening of the contacts ill, ii, the discharge of the magnetic field sets up a back electromotive force in the operating winding 6 which tends to produce arcing at the contacts, Due, however, to the provision of the non-inductive winding 1, the energy resulting from the discharge of the electric field is dissipated by the non-inductive winding and arcing at the contacts is suppressed. The protective winding 7 may Sun round the operating winding 6 and take the form of two equal and oppositely wound sections, the wire preferably being a fine resistance wire which gives the winding 1 a resistance several times that of the'operatlng winding 8. As shown in Fig. 2, the armature shaft 3 is carried by straps l3 which are secured to opposite sides of the outer ends of the core I, and a restoring spring I4 is connected between the armature 2 and core i to return the armature to normal position when current flow through the solenoid is interrupted or falls below a predetermined value. Due to the shape and arrangement of the pole faces 4 and 5, the cries-- tive air gap is comparatively small when the armature is in open position and decreases but slowly as the armature starts moving towards its closed position. Near "the limit of its'angular movement, however, an increasing. proportion of the flux traverses the pole face 4 and the part o eflicientfrom the standpoint of the current em- I ployed to hold the contacts closed, i. e., the. currcntrequired to move the armature to closed .reuilll'd to maintain the pull on the armature increases rapidly as the gap between the armature and this pole face closes. The spring I is so proportioned that the restoring force which it exerts also increases rapidly. during the final angular movement-oi the armature 2.- Due to'the relatively uniform tractim on the armature during the greater its movement, the relay is particularly greatly in excess of that which is armature in closed position. The pick-up" current may be as low position is not as but flfty per cent in excess of thecurrent required to hold the armature in closed position, thus dilfering materiallyirom known relays in which the pick-up current is from about three O, I are of the form illustrated in Fig. 2, and

this assembly is mounted upon a base I! of insulating material which is slotted to receive the end section of the core I. Mounting brackets are arranged at each side of the magnet, flanges II of the brackets being secured to the end section of the core i-while flanges I! rest upon and are secured to the upper face of the base it.

' Terminals I. for the double solenoid i, 1 are mounted at one end of-the base.

In this particular relay.

of gravity of the armature and switch assembly is substantially at the axis of the pivotal shaft 3 of the armature. when, as in the construction illustrated, the armature is supported atits center of gravity, the center of gravity of the switch and switch bracket assembly substantially coincides with the center of gravity of the armature. Since the switches are not lifted by the armature, but are tilted about their center of gravity, the relay will respond to a relatively'small amount of energy.

It will be apparent that one switch I! may be eliminated from'the relay shown in Figs. 3 and 4 if a control of only one auxiliary circuit is desired and that additional switches may be mounted on armature 2 when more than two circuits are to be controlled by the relay.

In the relay shown in Figs. 5 and 6, the magnet structure and base may be the same as that shown in Figs. 3 and 4, but a tapped solenoid is used to provide an' electrical locking relay. One switch ll, its mounting bracket 20 and terminal connections 21, 22 are also identical with that "of the described relay; this switch I! being included in the local circuit that is controlled by the relay. The switch bracket 23 terminates in'a flange 2! which is curved to the switch mochanism is designed to control two auxiliary cirprovide seats for two mercury switches 2" 25'', the switches being held in place by a clip 18 that is bolted to flange 24 of the bracket II. As shown in the wiring diagram that is superposed on the Fig. 6 view, the operating winding comprises two equal sections 8','-8", which are shunted by non-inductive windings 'I', 1, respectively. The control switch S includes a pair of contacts a, b between which the contact arm c moves. Contact arm -c is connected through a current source B to the relay input terminal ll= that leads to the center point of the windings, and contact a is connected through terminal I! to the end of section I of the solenoid. Flexible leads 21 extend from mercury switch 25' to the terminal I! and to a second terminal 28 that is connected to the contact arm c of the control switch. Mercury switch I!" is connected by flexible leads 21 to the end of the section 5". of the solenoid, and to a terminal 28* that is connected to contact b 01 the switch S. With the contact arm 0 .in neutral position, the solenoid is not energized and switches 25', 25 are both open, with switch I! either open or closed in accordance with the requirements oi the particular load circuit. When contact arm c engages contact a, the circuit is closed through winding .6", and the armature moves to closed position, closing switches 25 and 25. Switch 25 is in parallel with contacts a, c, and thereand therefore the closing of switch 25' enables the control switch to establish a current flow through the section 6 of the solenoid when contact cengages the contact 1:. Upon closing contacts b, c, the direction of current flow through section 6'' neutralizes the existing magnetic fleld, and armature 2 drops away, and opens switches 25', 25*, thus restoring the original conditions.

As shown in Figs. 7, 8, and 9, the switch isof the direct contact type and comprises a resilient contact arm 29 that is mounted on the armature 2, being insulated therefrom by washers 30, and connected by a flexible lead ll to the terminal 32. A contact 38 is mounted on base I! for engagement with contact arm 29 when the relay is not energized, and a second contact 34 is positioned for engagement with contact arm I! when the relay is energized, as shown in Fig. 'l.

The contact arm 28 engages the flxed contact ll before the armature 2 reaches its fully closed position, as shown in Fig. 9, and the final movement of the armature slides the contact arm 2!- over contact to provide a self-cleaning contact. The resilient contact arm 2! is flexed during this operation, resulting in a flrm engagement of the contacts and also in an increase in the force tending to return the armature 2 to open position, thus-offsetting a portion of the increase 'in magnetic pull which arises as the gap between and it will beapparent that physical embodiments of the invention may vary materially from those illustrated in the drawings without departing from the spirit of the invention as set forth in the following claims.

I claim:

1. An electromagnetic device of the type including a core having opposed poles, an armature of rectangular bar form between said poles,'switch mechanism mounted on said armature and forming therewith a moving system, means pivotally supporting said armature for rocking movement about an axis passing substantially through the center of gravity of said moving system, and an operating winding on said core, characterized by the fact that one of said poles includes a face positioned adjacent and substantially parallel to the path of movement of one end of said armature, and a face extending into the path of movement of said armature.

2. In an electromagnetic switch adapted to be controlled by a sensitive relay, a core having spaced poles, an armature, switch mechanism mounted on said armature and forming therewith a moving system, means supporting said armature for rocking movement in the gap between said poles and about an axis passing substantially through the center of gravity of said moving system, and a solenoid for establishing a magnetic field; one ofsaid poles being notched to provide angularly disposed surfaces adjacent the end face and a side face of said armature when the latter attains its solenoid-energized position.

3. The invention as set forth in claim 2, wherein the angularly disposed surface of said notched pole which is adjacent the end face of the armature is substantially coextensive with the said end face.

4. The invention as set forth in claim 2, in combination with spring-means opposing movement of said armature by the magnetic flux and presenting a greater force in opposition to the armature movement during the said final portion of the range of arcuate movement of the armature. v

5; In an electromagnet, a core having parallel sides and one end, a solenoid on said core, straps connecting the free ends of said core, a barshaped armature between and pivotally supported v the pivotal axis of said armature.

6. In an electromagnetic switch adapted to be controlled'by a sensitive relay, a laminated core having parallelside members joined by an end member, a solenoid on one of said members, a bar-shaped armature pivotally mounted at substantially its center for rocking movement in' the gap between the free ends of said members and movable into position substantially normal there to when said' solenoid is energized, the end of one of said side members being notched to provide a seat for receiving one end of said armature when the solenoid is energized,'and switch means mounted on said armature with its center of to provide a shoulder against which a side face of said armature seats when in closed position, and a tilting contact switch mounted on said armature, the said supporting means comprising a shaft located substantially at the rotational center of said armature and switch.

gravity substantially at, the pivotal axis of said 

